In the process for manufacturing a semiconductor device, for example, diffusion layers as source and drain regions are formed by ion-implanting a dopant. Then, annealing is performed to recover a defect caused by the ion implantation and to electrically activate the dopant (to decrease the resistance). Meanwhile, this annealing has such a problem that the ion-implanted atoms diffuse and expand the diffusion layers. Along with the recent advancement in miniaturization, such diffusion layers need to be formed as shallow as 50 nm or less. Since conventionally employed furnace anneal and RTA (Rapid Thermal Anneal) require long heating times and expand diffusion layers, annealing methods for applying high energy within a very short time are thus adopted.
As the annealing method, a flash lamp annealing method has been adopted which uses a flash lamp having a rare gas such as xenon sealed therein to apply pulsed light of 0.1 to 100 msec for heating. Furthermore, a laser annealing method has been recently studied which can further shorten the heating time by applying pulsed laser beam for 10 to 1000 nsec for heating.
Meanwhile, in the step of activating an impurity which is ion-implanted into the back surfaces of a power device IGBT (Insulated Gate Bipolar Transistor) and back-side illuminated image sensor, laser annealing is sometimes employed which can selectively heat only the back surface side within a short heating time so as to avoid thermal damage to a device layer on the front surface side (for example, Patent Document 1, Non Patent Document 1).
The laser annealing method forms a melted portion by laser irradiation, while a dopant can be activated by epitaxial growth utilizing a non-melted portion as a seed crystal (for example, Non Patent Document 1). Additionally, to increase the activation level, there have been proposed: a method in which laser beams with different pulse widths are combined for the activation (for example, Patent Document 2); and a method in which laser beams with different wavelengths are combined for the activation (for example, Patent Document 3).